Impurities occurring in diesel fuels can produce soluble and insoluble materials which are responsible for gum deposits and discoloration of the fuel. Other impurities may result from handling, corrosion of storage vessels and may even be introduced by the refiner to prevent or solve other problems with the fuel such as oxidation, rust promotion, etc. The end result can be the formation of deposits in the diesel engine, particularly with respect to the fuel injectors. The eventual result is poor engine performance with increased noise, starting problems and decreased power output and fuel economy. A primary purpose of this invention accordingly is to provide an additive for fuels, particularly diesel fuels, which will help reduce engine deposits. Another purpose of this invention is to provide an additive which will improve the stability and cleanliness of lube oil compositions.